There are two Wolgang Puck Express locations both at Downtown Disney. One is at the very furthest point of the MarketPlace and the other one is attached to Wolfgang Puck Cafe.
We ate at the MarketPlace location in August and the food was fantastic. I don't remember a specific child's menu but there was quite a large selection and I am sure you would find something you like. Check out Disboards Dining or All Ears Net for menus.